Tubes made of thin, flexible plastic are used for a range of different packaging purposes, such as packaging hygiene articles, cosmetics and foods. The contents of such tubes may consequently be, for example, soft cheese, caviar, hair-styling gel, toothpaste, shampoo, lotion or liquid soap. The tube should have a smart appearance so as to be visually appealing on the shop shelf. For hygiene articles and cosmetics, it is moreover important that the tube looks attractive and decorative, for example on a bathroom shelf. It is also important that the outside of the tube is of such a nature that product information is conveyed in a clear and easily understood way to a purchaser or user of the packaged product. For these reasons, tubes are usually provided with direct printing or a label which can be printed with the desired pattern and text.
One way of applying labels to containers is by what is known as “in-mould-labelling”, IML, that is to say by melting a label on at the same time as the container is formed by injection into a mould. IML affords a number of advantages, both with regard to the appearance of the finished container and during manufacture of the container. For example, it is possible to produce a glossy or matt label surface which can have the effect of giving the container an elegant appearance. It is also possible to reduce changeover times considerably when a label is changed, as a result of which shorter product runs can be manufactured at a reasonable cost and delivery times to the customer can be reduced.
It has consequently become increasingly common to apply labels to different types of injection-moulded container using the IML technique. However, it has proved to be difficult to achieve a good result with IML in the manufacture of injection-moulded thin-walled tubes as these require very great compressive forces and injection speeds which result in a high rate of breaking and other damage to the labels. In order not to have a negative effect on the flexibility of the tube, the material of the labels used moreover has to be very thin, which further increases the risk of the label breaking during tube manufacture. The small wall thickness of the tubes also means that the heat transfer from the plastic melt to the label is small, which means that the label has to be thin in order to be capable of being melted onto the tube during the manufacturing process.
As the IML technique affords many advantages, such as better pliability of the label around edges and irregularities on a container and a greater possibility of achieving full coverage of the container, it is desirable for it to be possible to use IML for thin-walled tubes as well.